This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall objective of this study is to evaluate the safety and efficacy of alternative dosing regimens of Myozyme in patients with Pompe disease who have not demonstrated an optimal response to the standard dosing regimen of 20 mg/kg every other week (qow) after a minimum of 6 months of regular treatment immediately prior to study entry. Eligible patients will be randomized on a 1:1 basis to a "frequent dosing group" (20 mg/kg every week [qw]) or a "high dose group" (40 mg/kg every other week [qow]) of Myozyme treatment.